An illustrated review of reticulated vitreous carbon (RVC) as an electrode material is presented. Early uses of RVC were largely restricted to small-scale (< 1 cm 3 ) electroanalytical studies in research laboratories. RVC properties of a high ratio of surface area to volume and minimal reactivity over a wide range of process conditions, combined with low cost and easy handling, have resulted in a steady diversification of its applications both in research laboratories and in industry. The physical structure of RVC (in terms of pores per linear inch, strut length, strut thickness and area of the trigonal strut) is examined for 10, 30, 60 and 100 ppi (pores per linear inch) grades using scanning electron microscopy. The accurate measurement of these geometrical values presents both theoretical (in terms of definition of trigonal strut area, beginning and end of single strand) and practical problems (large differences in strut length and thickness in individual samples). Data are presented to show the relationships between geometrical properties. Applications include electroanalytical studies and sensors, metal ion removal, synthesis of organics and FentonÕs reagent, H 2 O 2 production and batteries/fuel cells.

The limitations of 2-dimensional electrodes can be overcome by using threedimensional materials having sufficient porosity and active area while offering moderate mass transport rates and a relatively low pressure drop at controlled electrolyte flow rate. In concept, a wide variety of metal, ceramic and composite materials are possible but restrictions are imposed by the need to avoid materials degradation, while maintaining adequate electrical conductivity, sufficient robustness and the possibility of facile scale-up. Despite its fragility, one of the traditional electrode materials used as a porous, 3-dimensional electrode is carbon foam, particularly in the 97% vol. porous form of reticulated vitreous carbon, RVC. A timeline indicates that the history of this material dates back over 50 years to the mid1960s, when it was primarily used as an uncoated material in small-scale, laboratory electroanalysis. Surface modification and diverse coatings have considerably extended the use of RVC. Recent applications are found in sensors and monitors, electrosynthesis, environmental processing and energy conversion. This review highlights the fundamental structure and summarises the physicochemical properties of RVC. Fluid flow through various porosity grades of the material, their active electrochemical area and rates of mass transport are quantified. The diverse applications of RVC in energy conversion, environmental treatment and electrosynthesis are illustrated by selected examples from the authors' laboratories and others over the last 30 years. Recent research on coated RVC, energy conversion environmental remediation and sensors is highlighted. Critical areas deserving further research and development are proposed.

The characteristics of a divided, industrial scale electrochemical reactor with five bipolar electrodes (each having a projected area of 0.72 m 2 ) were examined in terms of mass transport, pressure drop and flow dispersion. Global mass transport data were obtained by monitoring the (first order) concentration decay of dissolved bromine (which was generated in situ by constant current electrolysis of a 1 mol dm −3 NaBr (aq) ). The global mass transport properties have been compared with those reported in the literature for other electrochemical reactors. The pressure drop over the reactor was calculated as a function of the mean electrolyte flow velocity and flow dispersion experiments showed the existence of slow and fast phases, two-phase flow being observed at lower velocities.

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Electrochemical techniques have an important role to play in many areas of environmental treatment, including clean synthesis, recycling of reagents, water purification, analysis and monitoring of species, removal of pollutants and recycling of materials. These overlapping subject areas cover a broad and vital range of industrial sectors and products. These considerations lead to the need for calculated 'performance indicators' for practical reactor geometries together with information on process experience with available reactor technology. This paper considers critical design features and figures of merit for electrochemical reactors that have been used in environmental treatment.